An actinomycete (Streptomyces setonii, isolate 'UFV-RD1'), isolated from the rhizosphere of a healthy tomato plant was selected out of 117 as a promising biocontrol agent for tomato diseases. In in vitro antagonism tests against tomato pathogens, the isolate 'UFV-RD1' was unable to inhibit growth of bacterial pathogens (Pseudomonas syringae pv. tomato, Ralstonia solanacearum, Pectobacterium carotovorum subsp. carotovorum, Xanthomonas campestris pv. vesicatoria) but inhibited conidium germination of fungi (Alternaria solani, Phytophthora infestans, Corynespora cassiicola, Stemphylium solani). Experimental biocontrol assays in a greenhouse indicated that the actinomycete was effective for reducing symptom severity in the case of bacteria and fungi tested as challenging pathogens. In field trials, when A. solani and P. infestans spontaneously occurred, plants resulting from seeds microbiolized with propagules of isolate 'UFV-RD1' showed less severe symptoms in the case of early blight. Therefore, the biocontrol agent is considered a good choice tobe included in future protocols of disease integrated management as a way to reduce defensive use.
Streptomyces setonii; microbial antagonism; induced resistance; biological control
